Crystalline resin compositions

ABSTRACT

Disclosed is a crystalline resin composition containing a nucleating agent composition comprising 
     (a) at least one of the dibenzylidene sorbitol and xylitol derivatives wherein either one of the aromatic rings has 2 or 3 methyl groups and the other is unsubstituted, 
     (b) at least one of dibenzylidene sorbitol and xylitol, and 
     (c) at least one of the dibenzylidene sorbitol and xylitol derivatives wherein each of the aromatic rings has 2 or 3 methyl groups, and the proportions of (a), (b) and (c) being such that Z calculated according to the equation 
     
         Z=A/(A+B+C) 
    
     wherein A, B and C are each the amount by weight of the components (a), (b) and (c), respectively, is within the range of about 0.3 to about 0.8.

The present invention relates to a crystalline resin composition andmore particularly to a crystalline resin composition which is improvedin processability and which can give a molded article improved intransparency, thermal and mechanical properties, and the like.

Dibenzylidene sorbitol compounds (hereinafter briefly referred to as"DBS compounds") which are prepared by condensing an aromatic aldehydeand sorbitol in the presence of an acid catalyst have been widely usedas nucleating agents for crystalline resin compositions. For providing anucleating agent more superior in properties to those conventionallyused, we have hitherto conducted intensive research and consequentlyhave proposed various kinds of DBS compounds.

However, since there is a demand for nucleating agents from many fields,there is still a room for improvement for the purpose of rendering themapplicable to a wide variety of uses.

More specifically, when 1,3:2,4-dibenzylidene sorbitol (hereinafterbriefly referred to as "DBS") is used, the resulting molded article ofcrystalline resin can be improved in optical characteristics,particularly in transparency to a large extent. Yet DBS does notsufficiently satisfy the demand of technical areas in which a higherdegree of transparency is needed.

To obviate such problem, we proposed1,3:2,4-di(methylbenzylidene)sorbitol (hereinafter simply referred to as"Me-DBS") which is prepared by using toluylaldehyde as a startingmaterial in place of benzaldehyde (Unexamined Japanese PatentPublication Nos. 117044/1978 and 28348/1979). Although a resin moldedarticle having a remarkably excellent transparency can be obtained withthe application of this compound, toluylaldehyde is commonly used alsoas a perfume and has a strong scent and therefore possesses the drawbackof being likely to readily exude an odor due to thermal decomposition ofthe nucleating agent during the molding of the resin composition withheating.

The use of 1,3:2,4-Bis(polyalkylbenzylidene)-sorbitol (UnexaminedJapanese Patent Publication No. 45934/1981) or so-called unsymmetricaltype DBS compounds wherein one of the aromatic ring has substituent(s)different from the other in kind and number (Unexamined Japanese PatentPublication No. 12951/1984) can give a crystalline resin compositionsuitable for the production of a molded article which is excellent intransparency as in the case of using Me-DBS, and can reduce to a largeextent the odor exuded during the molding with heating which is a defectof Me-DBS.

On the other hand, unlike conventional nucleating agents of "dispersiontype" such as metal salts, silica and the like, DBS compounds arenucleating agents of "dissolution type" which must be melted anduniformly dissolved in the resin at a temperature higher than themelting point thereof. Accordingly, when such DBS compound is used as anucleating agent, it is important to melt it for mixing with acrystalline resin at a high speed during the molding of the resin. Inview of this, the use of a nucleating agent having a high melting pointentails a disadvantage that the resin composition containing suchnucleating agent must be molded under a severe condition of hightemperature. For molding such resin composition at a temperature lowerthan the melting point of the nucleating agent, an additional step isnecessary beforehand in which the nucleating agent and the crystallineresin are melted by heating at a temperature higher than the meltingpoint of the nucleating agent to prepare a master batch of highconcentration. Therefore, the lower the melting point of the nucleatingagent to be used, the more superior the processability of thecrystalline resin composition containing the nucleating agent in themolding step.

However, our research revealed that with an increase in the meltingpoint of the nucleating agent, the crystalline resin compositioncontaining the agent tends to give a molded article having moreexcellent transparency and other properties although having the problemin processability. Therefore it is an antinomic and difficult problem toimprove the processability of the resin composition by using anucleating agent of low melting point and simultaneously to therebyenhance the transparency and other properties of the molded article.Furthermore, the conventional nucleating agents tend to sublime at or inthe neighborhood of the melting point thereof, and therefore soils orsmears the mold and molding equipment, thereby deteriorating theprocessability of the resin composition.

For example, a crystalline resin composition containing as a nucleatingagent said 1,3:2,4-bis(polyalkylbenzene)sorbitol or DBS compound of theunsymmetrical type mentioned above provides a molded article outstandingin transparency and like characteristics. Nevertheless, the nucleatingagent contained therein has a melting point of as high as 260° C. andthe resin composition must be molded usually at a high temperature. Forthis reason, in order to produce the above-mentioned remarkable effectof the nucleating agent of DBS compound in an ordinary molding fieldwherein a resin composition must be molded with heating only at atemperature of 260° C. or lower, there are entailed specificdifficulties such as, e.g., of necessitating an additional step ofpreparing a high concentration master batch at a temperature of notlower than the melting point of the nucleating agent used. Furthermore,the above nucleating agents did not solve the problem of mold soilingand resultant deterioration of processability or moldability of theresin composition due to sublimation of the nucleating agent duringmolding operation.

In view of the above, an object of the present invention is to provide acrystalline resin composition which can give a molded articleoutstanding in transparency and other properties and which can be moldedinto a desired product at a relatively low temperature due to the lowmelting point of the nucleating agent contained therein withoutentailing the problem of soiling of the mold and molding equipment.

The present invention provides a crystalline resin compositioncomprising

(i) a crystalline resin, and

(ii) a nucleating agent which comprises

(a) at least one of the compounds represented by the formula ##STR1##wherein R¹ is methyl, R² is hydrogen atom, and m is 2 or 3; or R₁ ishydrogen atom, R² is methyl, and n is 2 or 3; and p is 0 or 1,

(b) at least one of the compounds represented by the formula ##STR2##wherein p is 0 or 1, and (c) at least one of the compounds of theformula ##STR3## wherein r is the same and is an integer of 2 or 3, andp is 0 or 1, the proportions of the components (a), (b) and (c) to becombined being such that Z calculated according to the equation

    Z=A/(A+B+C)

wherein A, B and C are each the amount by weight of the components (a),(b) and (c), respectively, is within the range of about 0.3 to about0.8.

We conducted intensive research on properties of DBS compounds servingas nucleating agents for crystalline resins, and consequently found thata nucleating agent composition containing the above-specified components(a), (b) and (c) in a specific ratio is surprisingly low in meltingpoint compared with the similar known compounds and that the resincomposition containing this nucleating agent composition is not onlyimproved to a great extent in processability but also capable of givinga molded article excellent in transparency and other various properties.The present invention has been accomplished based on these findings.

According to the present invention, the following excellent advantagesare attainable.

(1) The resin composition of the present invention exudes substantiallyno odor during molding operation.

(2) The time required for molding cycle is shortened because of theincrease in crystallization temperature.

(3) Due to the low melting point of the nucleating agent composition ofthe invention, the resin composition can be molded at a low temperature,and furthermore the formation of fish-eye due to an incomplete meltingof the nucleating agent is precluded.

(4) The resin composition of the invention is moldable without formationof molding sink and also moldable, even when having dispersed therein apigment, without entailing volume shrinkage.

(5) Stretched films can be produced with an improved dimensionalstability from the resin composition of the invention.

(6) The molded article prepared from the resin composition of theinvention is improved in transparency to a large extent.

(7) The molded article is improved in gloss as well.

(8) The molded article is excellent also in mechanical and thermalproperties such as modulus of elasticity, impact resistance, heatdistortion temperature and the like.

(9) The nucleating agent composition according to the invention does notcause soiling or smearing of the mold and molding equipment due tosublimation during molding operation, thereby keeping the mold andmolding equipment substantially maintenance-free for a long time andfacilitating continuous molding of the resin composition of theinvention.

Typical examples of the component (a) which constitutes the nucleatingagent composition contained in the crystalline resin composition of theinvention are 1,3-dimethylbenzylidene-2,4-benzylidene sorbitol,1,3-trimethylbenzylidene-2,4-benzylidene sorbitol,1,3-benzylidene-2,4-dimethylbenzylidene sorbitol,1,3-benzylidene-2,4-trimethylbenzylidene sorbitol and the like. Themethyl group may be substituted on any position of the aromatic ring.The same thing can be said with regard to the derivatives describedhereinafter.

Specific examples of the compound serving as the component (b) includeDBS.

Useful as the compound serving as the component (c) are, for example,1,3-dimethylbenzylidene-2,4-dimethylbenzylidene sorbitol (hereinafterbriefly referred to as "bis-dimethyl-DBS"),1,3-trimethylbenzylidene-2,4-trimethylbenzylidene sorbitol and the like.

Also usable as the component for constituting the nucleating agentcomposition of the invention are various kinds of dibenzylidene xylitolswhich are prepared by the same procedure as employed for producing theabove-exemplified compounds with the exception of using xylitol in placeof sorbitol as the polyhydric alcohol to be used as the startingmaterial.

In each of the components (a), (b) and (c), one or at least twocompounds in the form of a mixture can be suitably selected for use.However, the melting point-depressing effect and the utmost productionof the function of the nucleating agent, both peculiar to the presentinvention, can not satisfactorily be achieved at the same time unless Zis within the range of about 0.3 to about 0.8, preferably about 0.4 toabout 0.75.

In other words, it is important in the present invention that thecomponent (a) be present in an amount of not less than about 30% byweight and not more than about 80% by weight in the nucleating agentcomposition. The amounts of the components (b) and (c) in the nucleatingagent composition are not specifically limited and each can be selectedover a wide range provided that Z is within the range of about 0.3 toabout 0.8. In this limitation, none of the amounts of the components (b)and (c) are 0% by weight.

In the present invention, a satisfactory result can generally beattained by using the component (a) in an amount of about 30 to about80% by weight, preferably about 40 to about 75% by weight, the component(b) in an amount of about 1 to about 30% by weight, preferably about 5to about 25% by weight, and the component (c) in an amount of about 5 toabout 60% by weight, preferably about 10 to about 50% by weight, eachbased on the weight of the nucleating agent composition, the proportionsof the components (a), (b) and (c) being selected such that Z is withinthe range of about 0.3 to about 0.8.

Each of the components (a), (b) and (c) is a known compound and can bereadily prepared according to a conventional method. Accordingly, thenucleating agent composition according to the invention can be preparedby admixing the components (a), (b) and (c) in the above-specifiedmixing ratio. Further, the components (a), (b) and (c) can be producedall at once in the above-specified ratio by reacting sorbitol or xylitolwith an appropriate mixture of benzaldehyde and di- ortrimethylbenzaldehyde. A specific example of this preparation methodwill be described in Preparation Example below.

The above-specified nucleating agent composition according to theinvention is a novel one as a nucleating agent for crystalline resins.Therefore, the present invention also provides a nucleating agentcomposition which contains the above components (a), (b) and (c) in saidspecific ratio.

The amount of the nucleating agent composition according to theinvention to be incorporated into the crystalline resin is not limitedspecifically and can be suitably determined over a wide range insofar asthe contemplated effects are attainable. Usually, the nucleating agentcomposition is used in an amount of about 0.05 to about 3 parts byweight, preferably about 0.07 to 1 part by weight, per 100 parts byweight of the resin. The use of the nucleating agent composition in anamount within said range produces the contemplated effects of theinvention to a full extent.

As the method for addition of the nucleating agent to the resin, it ispreferable to use the single-stage addition method wherein thenucleating agent composition is added to the resin directly. However,two-stage addition method can also be employed wherein the agent isadded in the form of a master batch having a high concentration of about2 to about 15% by weight.

Examples of the crystalline resin to which the nucleating agentcomposition of the invention is added are crystalline polyolefin resinssuch as polyethylene resins, polypropylene resins and polybutadieneresins, polybutene resins, methylpentene resins and the like. Typicalexamples thereof are high density polyethylene, medium densitypolyethylene, linear low density polyethylene, ethylene copolymercontaining at least 50% by weight of ethylene, propylene homopolymer,propylene copolymer containing at least 50% by weight of propylene,butene homopolymer, butene copolymer containing at least 50% by weightof butene, methylpentene homopolymer, methylpentene copolymer containingat least 50% by weight of methylpentene, polybutadiene, etc. Theabove-exemplified copolymers may be either random copolymers or blockcopolymers. Specific examples of the comonomers constituting thecopolymers are C₂ -C₁₆ α-olefins such as ethylene, propylene, butene,pentene, hexene, heptene, octene, nonene, decene, undecene dodecene andthe like; acrylic or methacrylic acid esters, particularly C₁ -C₁₈ alkylesters, such as methyl acrylate, methyl methacrylate, ethyl acrylate,ethyl methacrylate, butyl acrylate, butyl methacrylate, octyl acrylate,octyl methacrylate, stearyl acrylate, stearyl methacrylate and the like;vinyl acetate; etc.

Various additives can also be suitably incorporated into the resincomposition of the invention according to its specific application or apurpose of use. Useful as such additives are antioxidant,thermostabilizer, ultraviolet absorber, lubricant, cross-linking agent,cross-linking promoter, foaming agent, coloring agent, dispersant,filler, antistatic agent, etc.

The molded article of the resin composition of the invention can beproduced by any of suitable processes heretofore known. For example, themolded article can be prepared by blending the crystalline resindirectly with the nucleating agent composition of the invention in whichthe above-mentioned components are combined in the specific ratio andmolding the resulting mixture into the desired product, or byincorporating the nucleating agent into the resin beforehand,pelletizing the mixture, and thereafter molding the same into thedesired molded product.

Any of conventional molding methods can be employed to mold the resincomposition of the invention. Illustrative of such molding methods areinjection molding, extrusion molding, blow molding, vacuum molding,rotational molding film molding, etc.

EXAMPLES

The present invention will be described below in greater detail withreference to the following Examples and Comparative Examples in which"part(s)" and "%" mean "part(s) by weight" and "% by weight",respectively, unless otherwise indicated.

In each Examples and Comparative Examples, the evaluation of eachproperty was conducted according to the following methods.

The melting point (mp) of the DBS compound is an endothermic peaktemperature determined by heating the compound with use of adifferential scanning calorimeter while elevating the temperature at arate of 20° C./min starting from room temperature.

On the other hand, in evaluation of the properties of the molded articleprepared from the crystalline resin composition, haze (%) according toJIS K-6714 and gloss (60°, %) according to JIS Z-8741 were measured atthe same time with use of a hazemeter. The smaller the haze is and thelarger the gloss is, the more excellent the optical characteristics ofthe resin composition are.

Further, using a differential scaning calorimeter, the temperature (Tc)(°C.) at which resin is crystallized (hereinafter referred to as"crystallization temperature") was determined while cooling the moltenresin composition having a temperature of 240° C. at a rate of 20°C./min. The higher the Tc is, the more excellent moldability thecomposition has, and typically the molding cycle can be shortened ininjection molding.

The flexural modulus of the molded sheet was measured according to JISK-7203-1982, and expressed in terms of a relative value based on thevalue of the resin sheet containing no nucleating agent.

The degree of evolution of odor was evaluated by hermetically sealing 30g of the pellets in a 200 ml glass bottle, allowing the bottle to standin a constant-temperature chamber maintained at 130° C. for 1 hour andjudging the presence or absence of the odor.

None: No odor, Odor: Odor is present.

Using the pellets prepared in each of examples and comparative examples,continuous injection molding of a sheet (10 mm×40 mm×40 mm) wasconducted until the mold soiling appeared, and the number of shots (Nc)by which the mold soiling appeared was recorded.

PREPARATION EXAMPLE 1

A 36.4 g (0.2 mol) quantity of powdery sorbitol, 26.8 g (0.2 mol) of2,4-dimethylbenzaldehyde, 21.2 g (0.2 mol) of benzaldehyde, 300 ml ofcyclohexane, 20 ml of dimethylformamide and 0.7 g of a concentratedsulfuric acid were charged into a 3 l four-necked flask equipped with acondenser with decanter, a thermometer, a gas inlet and a stirrer. Theair in the system was replaced with nitrogen. The resulting mixture washeated with stirring and the water produced by condensation wasdistilled off while maintaining the whole reaction system at atemperature of 70° to 80° C. The reaction was continued for 4 hours andthe reaction mixture was neutralized, washed with water and dried,giving a nucleating agent composition (nucleating agent composition No.I, Z=0.64) having a formulation as shown in Table 1 in a yield of 85%.The composition was analyzed by means of gas chromatography. Thecomponent (a) is a mixture of a compound of the formula (I) wherein R¹is H, R² is CH₃, n is 2 and p is 1 and a compound of the same formulawherein R¹ is CH₃, R² is H, m is 2 and p is 1. The component (b) is DBSand the component (c) is bis-dimethyl-DBS.

EXAMPLE 1

To 100 parts of random polypropylene resin containing 2% by weight ofethylene and having a melt index of 12 were added 0.3 part of thenucleating agent composition obtained in Preparation Example 1, 0.1 partoftetrakis[methylene-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]methane(trade name, "Irganox 1010," product of Chiba-Geigy Corp.) and 0.05 partof calcium stearate and the mixture obtained was stirred with Henschelmixer at a speed of 750 rpm for 3 minutes. Then the mixture was kneadedand extruded with Labo-Plast Mill to produce pellets by water coolingand cutting method. The pellets were press-molded at 230° C., giving asheet 1.5 mm in thickness for use as a specimen. The results are shownin Table 2.

EXAMPLES 2 TO 6

The compounds which are the components of the nucleating agentcomposition I were each prepared separately and admixed together in aspecific ratio to give nucleating agent compositions listed in Table 1(nucleating agent compositions Nos. II to VI). The properties of theresin compositions having incorporated therein the foregoing nucleatingagent compositions, and those of the sheets obtained from the resincompositions were evaluated following the procedure of Example 1. Table2 shows the results.

COMPARATIVE EXAMPLES 1 TO 6

In order to demonstrate the remarkable effects originating from the useof the specific formulation according to the invention, resincompositions and sheets both containing comparative nucleating agentcompositions of a variety of formulations (nucleating agent compositionsNos. VII to XII) were prepared following the procedure of Example 1. Theproperties of the compositions and the sheets were evaluated with theresults shown in Table 2.

COMPARATIVE EXAMPLE 7

In order to demonstrate that the molded article obtained from the resincomposition which has incorporated therein the nucleating agentcomposition of the invention has an excellent transparency, a resincomposition and a sheet containing Me-DBS which was hitherto consideredto produce the most outstanding effect of imparting transparency to theresin were prepared in the same manner as in Example 1. The propertiesof the composition and sheet were evaluated. Table 2 shows the results.

COMPARATIVE EXAMPLE 8

Following the procedure of Example 1, the properties of the resin inwhich DBS compound is not incorporated as a nucleating agent, and thoseof the sheet obtained from the resin in the same manner as in Example 1were both evaluated. Table 2 shows the results.

EXAMPLE 7

Resin composition and sheet were produced according to the method ofExample 1 with the exception of using linear low density polyethylene,using the nucleating agent composition in an amount of 0.2 part per 100parts of the resin and adjusting the temperature in the extruder to 220°C. The properties of the thus-obtained resin composition and sheet wereevaluated. The results are shown in Table 3.

EXAMPLES 8 TO 12

Resin compositions and sheets in which the nucleating agent compositionsof the invention (Nos. II to VI, listed in Table 1) were incorporatedwere produced following the procedure of Example 7. The properties ofthe resin compositions and the sheets were evaluated. Table 3 shows theresults.

COMPARATIVE EXAMPLES 9 TO 14

In order to show the noticeable effects derived from the specificformulation according to the invention, resin compositions and thesheets containing comparative nucleating agent composition of variousformulations (nucleating agent composition Nos. VII to XII) wereprepared according to the method of Example 7, and the properties of theresin compositions and the sheets were evaluated. Table 3 shows theresults.

COMPARATIVE EXAMPLE 15

Resin composition having Me-DBS incorporated therein was producedaccording to the method of Example 7 and sheet was prepared in the samemanner as in Example 7. The properties of the resin composition and thesheet were evaluated. The results are shown in Table 3.

COMPARATIVE EXAMPLE 16

A resin in which DBS compound is not incorporated as a nucleating agentand sheets obtained from the resin in the same manner as in Example 7were both evaluated for their properties. Table 3 shows the results.

                  TABLE 1                                                         ______________________________________                                        Nucleating                                                                             Proportions of     Mixing  Melting                                   agent compo-                                                                           nucleating agent* (wt %)                                                                         ratio   point                                     sition No.                                                                             A        B        C      Z     (mp, °C.)                      ______________________________________                                        I        63.7      9.6     26.7   0.64  228                                   II       66.1     20.1     13.8   0.66  229                                   III      30.0     30.0     40.0   0.30  229                                   IV       50.0     30.0     20.0   0.50  228                                   V        70.0     15.6     14.4   0.70  229                                   VI       80.0     10.0     10.0   0.80  229                                   VII      10.0     38.0     52.0   0.10  245                                   VIII     24.0     16.0     60.0   0.24  238                                   IX       90.0      4.0      6.0   0.90  248                                   X        100.0    --       --     --    262                                   XI       --       100.0    --     --    220                                   XII      --       --       100.0  --    262                                   ______________________________________                                         *Note:                                                                        A: a mixture of a compound (I) wherein R.sup.1 = H, R.sup.2 = dimethyl an     a compound (I) wherein R.sup.1 = dimethyl, R.sup.2 = H (p = 1 in each         compound)                                                                     B: DBS,                                                                       C: bisdimethyl-DBS                                                       

                                      TABLE 2                                     __________________________________________________________________________    Nucleating                                                                    agent com-   Properties of sheet Continuous                                   position     Haze                                                                             Gloss                                                                             flexural                                                                           Tc Odor of                                                                            moldability                                  No.       Z  (%)                                                                              (%) modulus                                                                            (°C.)                                                                     pellets                                                                            Nc                                           __________________________________________________________________________    Ex. 1                                                                             I     0.64                                                                             20 109 151  124                                                                              None >1500                                        Ex. 2                                                                             II    0.66                                                                             20 108 147  124                                                                              None >1500                                        Ex. 3                                                                             III   0.30                                                                             22 107 151  124                                                                              None >1500                                        Ex. 4                                                                             IV    0.50                                                                             21 109 145  124                                                                              None >1500                                        Ex. 5                                                                             V     0.70                                                                             20 108 150  124                                                                              None >1500                                        Ex. 6                                                                             VI    0.80                                                                             22 106 152  123                                                                              None >1500                                        Comp.                                                                             VII   0.10                                                                             40 102 135  120                                                                              None 550                                          Ex. 1                                                                         Comp.                                                                             VIII  0.24                                                                             29 101 140  121                                                                              None 705                                          Ex. 2                                                                         Comp.                                                                             IX    0.90                                                                             28 101 138  120                                                                              None 695                                          Ex. 3                                                                         Comp.                                                                             X     -- 30 100 135  120                                                                              None 700                                          Ex. 4                                                                         Comp.                                                                             XI    -- 35 102 134  119                                                                              None 450                                          Ex. 5                                                                         Comp.                                                                             XII   -- 25 107 140  122                                                                              None 800                                          Ex. 6                                                                         Comp.                                                                             Me-DBS                                                                              -- 23 107 150  123                                                                              Odor 730                                          Ex. 7                                                                         Comp.                                                                             blank -- 50  82 100  103                                                                              None >1500                                        Ex. 8                                                                         __________________________________________________________________________

                                      TABLE 3                                     __________________________________________________________________________           Kind of                                                                       nucleating agent                                                              Nucleating                                                                              Properties of sheet                                                 agent compo-                                                                            Fish-                                                                              Haze                                                                             Gloss                                                                             Tc Odor of                                              sition No.                                                                           Z  eye  (%)                                                                              (%) (°C.)                                                                     pellets                                       __________________________________________________________________________    Ex. 7  I      0.64                                                                             None 32 100 120                                                                              None                                          Ex. 8  II     0.66                                                                             None 32 101 120                                                                              None                                          Ex. 9  III    0.30                                                                             None 33 101 116                                                                              None                                          Ex. 10 IV     0.50                                                                             None 33 100 119                                                                              None                                          Ex. 11 V      0.70                                                                             None 32 102 120                                                                              None                                          Ex. 12 VI     0.80                                                                             None 33 100 120                                                                              None                                          Comp. Ex. 9                                                                          VII    0.10                                                                             Fish-eye                                                                           67  88 111                                                                              None                                          Comp. Ex. 10                                                                         VIII   0.24                                                                             None 42  90 112                                                                              None                                          Comp. Ex. 11                                                                         IX     0.90                                                                             Fish-eye                                                                           45  89 110                                                                              None                                          Comp. Ex. 12                                                                         X      -- Fish-eye                                                                           48  88 110                                                                              None                                          Comp. Ex. 13                                                                         XI     -- None 37  90 115                                                                              None                                          Comp. Ex. 14                                                                         XII    -- Fish-eye                                                                           36 102 115                                                                              None                                          Comp. Ex. 15                                                                         Me-DBS -- Fish-eye                                                                           35 101 115                                                                              Odor                                          Comp. Ex. 16                                                                         blank  -- None 79  83 104                                                                              None                                          __________________________________________________________________________

The sheet molded from the crystalline resin composition comprising thenucleating agent composition of the invention has the utmost degree oftransparency and gloss, and the resin composition does not evolve odordue to thermal decomposition during the molding. Further, the meltingpoints of these nucleating agent compositions are not more than 229° C.and thus noticeably low as compared with known DBS compounds, therebymaking it possible to mold the resin composition at a lower temperature.For this reason, it is easy to suppress the occurrence of fisheye owingto an incomplete melting of DBS compounds used as nucleating agents evenin the case of their addition to polyethylene or like resins which aremolded at relatively low temperatures. Moreover, the crystalline resincompositions according to the invention each have a high crystallizationtemperature (Tc), hence excellent in moldability.

EXAMPLE 13

Six kinds of nucleating agent compositions according to the inventionare prepared by mixing (a) a mixture of1,3-trimethylbenzylidene-2,4-benzylidene sorbitol and1,3-benzylidene-2,4-trimethylbenzylidene sorbitol, (b) DBS and (c)1,3:2,4-bis(trimethylbenzylidene) sorbitol, each of the compositionshaving the formulation corresponding to nucleating agent compositions Ito VI according to Examples 1-6, respectively.

Each of the nucleating agent compositions obtained above is blended witha crystalline olefin resin in the same manner as in Examples 1 to 6, andthe resulting crystalline resin compositions of the invention, whenmolded, can give molded articles which are substantially comparable tothe molded articles of Examples 1-6 in Tc, haze, gloss, flexuralmodulus, continuous moldability and other properties.

EXAMPLES 14

Six kinds of nucleating agent compositions according to the inventionare prepared by mixing (a) a mixture of 1,3-trimethylbenzylidene-2,4benzylidene xylitol and 1,3-benzylidene-2,4-trimethylbenzylidenexylitol, (b) dibenzylidene xylitol and (c)1,3:2,4-bis(trimethylbenzylidene) xylitol, each of the compositionshaving the formulation corresponding to nucleating agent compositions Ito VI according to Examples 1-6, respectively.

Each of the nucleating agent compositions obtained above is blended witha crystalline olefin resin in the same manner as in Examples 1 to 6, andthe resulting crystalline resin compositions of the invention, whenmolded, can give molded articles which are substantially comparable tothe molded articles of Examples 1-6 in Tc, haze, gloss, flexuralmodulus, continuous moldability and other properties.

EXAMPLE 15

Six kinds of nucleating agent compositions according to the inventionare prepared by mixing (a) a mixture of 1,3dimethylbenzylidene-2,4-benzylidene xylitol and1,3-benzylidene-2,4-dimethylbenzylidene xylitol, (b) dibenzylidenexylitol and (c) 1,3:2,4-bis(dimethylbenzylidene) xylitol, each of thecompositions having the formulation corresponding to nucleating agentcompositions I to VI according to Examples 1-6, respectively.

Each of the nucleating agent compositions obtained above is blended witha crystalline olefin resin in the same manner as in Examples 1 to 6, andthe resulting crystalline resin compositions of the invention, whenmolded, can give molded articles which are substantially comparable tothe molded articles of Examples 1-6 in Tc, haze, gloss, flexuralmodulus, continuous moldability and other properties.

We claim:
 1. A nucleating agent composition which comprises(a) at leastone of the compounds represented by the formula ##STR4## wherein R¹ ismethyl, R² is hydrogen atom, and m is 2 or 3; or R¹ is hydrogen atom, R²is methyl, and n is 2 or 3; and p is 0 or 1, (b) at least one of thecompounds represented by the formula ##STR5## wherein p is 0 or 1, and(c) at least one of the compounds of the formula ##STR6## wherein r isthe same and is an integer of 2 or 3, and p is 0 or 1, the proportionsof the components (a), (b) and (c) to be combined being such that Zcalculated according to the equation

    Z=A/(A+B+C)

wherein A, B and C are each the amount by weight of the components (a),(b) and (c), respectively, is within the range of about 0.3 to about0.8.
 2. A nucleating agent composition as defined in claim 1 whichcontains, based on the total amount thereof,the component (a) in anamount of about 30 to about 80% by weight, the component (b) in anamount of about 1 to about 30% by weight, and the component (c) in anamount of about 5 to about 60% by weight.
 3. A nucleating agentcomposition as defined in claim 1 which contains, based on the totalamount thereof,the component (a) in an amount of about 40 to about 75%by weight, the component (b) in an amount of about 5 to about 25% byweight, and the component (c) in an amount of about 10 to about 50% byweight.
 4. A nucleating agent composition as defined in claim 1 whichconsists essentially of(a) about 30 to about 80% by weight of at leastone of the compounds of the formula (I) wherein R¹ is methyl, R² ishydrogen atom, and m is 2; or R₁ is hydrogen atom, R² is methyl, and nis 2; and p is an integer of 1, (b) about 1 to about 30% by weight ofdibenzylidene sorbitol and (c) about 5 to about 60% by weight of1,3:2,4-bis(dimethylbenzylidene) sorbitol.